DIY light source for 10X10" enlarger.

"Stefan Patric" wrote in message
...

JJS,

IIRC, one of the Ansel Adams Photo Series books from years ago had
detailed instructions on how Adams built a diffusion head light source
for a horizontal enlarger made from a salvaged 8x10 camera. [...]

Oh, darn. That means I can get off my butt, walk 10 yards and get it right
now. I'm in the library at this moment.

Thanks, really, I didn't know he did that. Couldn't hoit! Will do.

Location/Available: Main Library Main Collection Call #: TR145 .A38 bk.3
Author: Adams, Ansel, 1902-
Title: The print / Ansel Adams with the
collaboration of Robert Baker.
Edition: 1st pbk. ed.
Publisher: Boston : Little, Brown, 1998.
Physical Details: x, 210 p. : ill. ; 25 cm.
Series Title: ( Ansel Adams photography series ; bk. 03)
General Note: Includes index.
Reprint. Originally published: Boston : Little, Brown, 1983.
Local Note MSF FY00

"Nicholas O. Lindan" wrote in message
m...
[... snip good stuff ...]
Nicholas O. Lindan, Cleveland, Ohio
Darkroom Automation: F-Stop Timers, Enlarging Meters
http://www.darkroomautomation.com/index2.htm

I hope the F-Stop timer can handle the bazillion watts I'm gonna put through
it with this thing. (Joking)

"Richard Knoppow" wrote.

I have no idea of what differences there are in the balasts [for cold
light enlarger heads] other than to withstand intermittent operation.

Fluorescent lamps are one variety of gas-discharge lamp.
They share their major electrical characteristic - negative
resistance - with HID/Mercury/Sodium lamps. Negative
resistance means that as the lamp current increases the
lamp voltage decreases and thus the current, unless
limited, quickly rises to near infinity (i.e., a lightning
bolt discharge). The ballast's purpose is to limit the
lamp current.

Graphic arts systems use several types of specialty
ballasts. Many use a combination of these features:

o Keep light output constant:

Regulating ballasts wherein the ballast uses a saturating
core reactor and works, with the power factor capacitor and
the lamp, as a ferroresonant regulator.

o Quickly come up to full brightness:

Ballasts having a low open circuit voltage
and a low reactance. This increases the current through
a cold lamp so that it warms faster. The lamps are
low voltage/low pressure designs with heavy duty electrodes
that can withstand the higher current without erosion.

o Keep the lamp warm so it comes up to full brightness
instantly:

Multi-level ballasts wherein the lamp idles at low power
in a keep warm state with the shutter closed and then
switches to high power with an open shutter to make the
exposure. Fan speed is reduced when the lamp is idling
at low power to keep the lamp at a hot operating temperature.

This feature is usually combined with the ability to run
the lamp at several power levels.

o Extend lamp life, especially where lamps cost many hundreds
of dollars:

Very low crest factor (Ipeak/Irms) ballasts than keep the
electrodes from wearing out. Electrode erosion is roughly
proportional to the cube of the current.

I don't know that the Aristo equipment is sophisticated enough
to use any of the above technologies.

Crest factor is main difference in the quality of a fluorescent
ballast. The ballasts in $10 work luminaries have a high
crest factor, leading to short lamp life and low light output
for power in. A high quality low crest factor ballast first
raises the voltage with an auto-transformer and then limits
the current with either inductive or capacitive reactance.
Often the some of the ballast reactance is supplied by
air-gapping or shunting the transformer to increase the leakage
inductance; often a capacitor is used for ballast reactance
and leakage inductance is used for power factor correction.
Additionally, the efficiency of the ballasts of high quality
ballasts is higher: thicker copper wire in the reactor/transformer
windings to keep resistive losses low, the prescience of power
factor correction capacitors and the use of low ESR capacitors.

For a garage work bench lamp all of this is of little concern:
the electricity savings of an efficient ballast will never
pay for its higher initial cost.

Aristo lamps are low current, high voltage, low pressure
mercury with a phosphor coating - sort of a hybrid between
a neon and a fluorescent lamp. The ballast is specific
to such a lamp and is, I am sure, a high quality low-crest
factor design.

If you are designing a cold light head using off-the-shelf
fluorescents you should look for the highest quality ballasts.
Long lamp life equates with stable light output.

The best economical high performance ballast systems, designed
for office/factory use, aren't applicable to cold-light heads.
Office lighting systems usually supply a high (and usually
bizarre - 347 volts anyone?) voltage from a central
step-up transformer with individual inductive ballasts
at each lamp. If power factor capacitors are used they
are often central with the transformer.

Much more than anyone in r.p.d., including myself, would
(or should) ever want to know.

--
Nicholas O. Lindan, Cleveland, Ohio
Darkroom Automation: F-Stop Timers, Enlarging Meters
http://www.darkroomautomation.com/index2.htm
n o lindan at ix dot netcom dot com

"Nicholas O. Lindan" wrote in message
m...
"jjs" jjs.jjs.net wrote
"Nicholas O. Lindan" wrote
Darkroom Automation: F-Stop Timers, Enlarging Meters
http://www.darkroomautomation.com/index2.htm

I hope the F-Stop timer can handle the bazillion watts I'm gonna put
through it with this thing. (Joking)

The standard F-Stop timer can only handle up to 2.3 quintillion watts,
5A or 300W incandescent - whichever comes first.

Hold on. I don't know anything about electricity. I just got it installed.
All I know is that it really hurts to stick yer tongue into the light
sockekt. It makes me ferget things. Like not to do it again.

So, if I put up to 1000@ into that head and plug it into the F-Stop timer,
it's going to go up in smoke? What do I do? (Besides do another DIY Electro
Convulsive Therapy thing.)

John

"Nicholas O. Lindan" wrote in message
m...
"jjs" jjs.jjs.net wrote
"Nicholas O. Lindan" wrote
Darkroom Automation: F-Stop Timers, Enlarging Meters
http://www.darkroomautomation.com/index2.htm

I hope the F-Stop timer can handle the bazillion watts I'm gonna put
through it with this thing. (Joking)

The standard F-Stop timer can only handle up to 2.3 quintillion watts,
5A or 300W incandescent - whichever comes first.

Auxiliary contactors are available for use up to 100 amperes.

The largest light source we make equipment for is 1 terrawatt @
100 megamps. https://lasers.llnl.gov/


Seriously, are you saying that there is a 100A contactor for the F-stop
timer? And if so, what sort of enlarger would use a 100A light source?

"Richard Knoppow" wrote

If one uses an enlarging meter the variations of fluorescent lamps with
temperature is of much less importance.

If only it were so.

The problem of lamp warming isn't mitigated by a meter - there
is the same variation in lamp output between metering
and exposing as there is between pre-warming and exposing.

A meter will compensate for slow variations due to lamp
aging, room temperature variation, and seasonal or dinural
voltage fluctuation.

A compensating timer/light integrator in combination with
an enlarging meter is a self-defeating mess: The effect is
to double the error and to do it in the wrong direction - the
dimmer the lamp the more overexposed the resulting print.
If the lamp dims the meter will indicate more exposure
is needed - the integrator will extend the exposure time
on it's own to compensate for the dim lamp and as a result
compensation is applied twice - a 10% dimming of the lamp
will result in a 10% over exposure to the material.

The only real solution for cold-light woes is to stabilize
the light output with either a closed-loop regulated head
or some means of keeping the lamp at a constant operating/
idling/off temperature.

--
Nicholas O. Lindan, Cleveland, Ohio
Darkroom Automation: F-Stop Timers, Enlarging Meters
http://www.darkroomautomation.com/index2.htm
n o lindan at ix dot netcom dot com

"jjs" jjs.jjs.net wrote
"Nicholas O. Lindan" wrote
Darkroom Automation: F-Stop Timers, Enlarging Meters
http://www.darkroomautomation.com/index2.htm

I hope the F-Stop timer can handle the bazillion watts I'm gonna put
through it with this thing. (Joking)

The standard F-Stop timer can only handle up to 2.3 quintillion watts,
5A or 300W incandescent - whichever comes first.

Auxiliary contactors are available for use up to 100 amperes.

The largest light source we make equipment for is 1 terrawatt @
100 megamps. https://lasers.llnl.gov/

--
Nicholas O. Lindan, Cleveland, Ohio
Darkroom Automation: F-Stop Timers, Enlarging Meters
A Unit of Cleveland Engineering Design, LLC
http://www.darkroomautomation.com/index2.htm
n o lindan at ix dot netcom dot com

"jjs" jjs.jjs.net wrote

So, if I put up to 1000@ [sic, watts?] into that head

Seriously -- if you want to control a 1KW head it
isn't any problem. You will need an auxilliary
contactor - a metal box with a relay in it -
that plugs into the (220V ?) power and the
timer. You then plug the enlarger into the
contactor box. Not mine, but:
http://www.largeformatphotography.in...3&d=1202624791

Darkroom Automation can supply contactor boxes
if you don't want to make your own.

The situation is the same with all timers.
Most giant enlargers have their own electronics
for running the head and the servo motors and also
have their own timer -- in this case the
contactor is built into the enlarger's power supply.

If you have an old HID head or a shuttered head
then the timer connects to the shutter and the
lamp power is a non-issue.

If you are making a custom 1 KW head you may
find yourself involved in making a power supply
for it. You would then have a contactor as
an integral part of the supply.

If you buy a 1KW stand-alone head it more than
likely has the contactor built into it or the
contactor is an integral part of the head 'kit'.

I am sure you have seen this thread ... Durst 10x10 enlarger:
http://www.largeformatphotography.in...ad.php?t=32852

--
Nicholas O. Lindan, Cleveland, Ohio
Darkroom Automation: F-Stop Timers, Enlarging Meters
http://www.darkroomautomation.com/index2.htm
n o lindan at ix dot netcom dot com

"Ken Hart" wrote in message
news:bAwLj.6181$N62.5248@trndny07...

Seriously, are you saying that there is a 100A contactor for the F-stop
timer? And if so, what sort of enlarger would use a 100A light source?

Typo. I meant 100W (see how close @ is to W?)
I have no idea what that means in Amps.

Nicholas O. Lindan wrote:



The multi-contrast gel filters add red light for better visibility
when dodging and burning -
red + blue = magenta
red + green = yellow

Ah ha - my confusion answered - so simple when you find out why.

--
http://www.petezilla.co.uk